1. Field of the invention
This invention relates to an element for electrophoresis, and more particularly relates to an element for electrophoresis suitably employable for electrophoresis of biopolymers such as proteins.
2. Description of prior arts
The electrophoresis can be carried out in the following manner: a membrane medium for electrophoresis prepared by coating or casting a membrane-forming material such as agar, cellulose, cellulose acetate, starch, silica gel or polyacrylamide gel over a support such as a glass plate or transparent plastic sheet (or film) is impregnated with a buffer solution; on the medium is applied a substance to be analyzed (sample); the applied sample is developed (or resolved) on or in the medium by applying a voltage between the both ends of the support and dyed thereon; and then the dyed sample is measured on the optical density to quantitatively determine the components of the sample.
Details of the electrophoresis and medium therefor are given in "Experimental Text for Electrophoresis (5th revision)" editted by Electrophoresis Society of Japan (Bunkodo, 1975), "Modern Electrophoresis" editted by Aoki & Nagai (Hirokawa Shoten, 1973), etc.
Recently, the electrophoresis has been employed to analyze substances originating from a living body; for instance, the analyses of proteins originating from a living body are generally performed in the course of biochemical analysis for diagnosis.
As the membrane or sheet for electrophoresis, a filter paper was previously employed, but recently an agarose membrane or a polyacrylamide gel membrane (or medium) has been employed from the viewpoints of their advantageous properties. Particularly, the polyacrylamide gel membrane showing melecular sieve function is widely employed recently. The polyacrylamide gel membrane can be prepared by crosslinking polymerization of a monomer such as acrylamide and a two-functional crosslinking agent such as N,N'-methylenebisacrylamide under an oxygen-free condition in the presence of water and a polymerization catalyst.
In the course of the preparation of the polyacrylamide gel membrane, a modifier such as an anionic surfactant is incorporated into the membrane in certain cases. Since only a small amount of the modifier is required for the preparation of the gel membrane for protein analysis, the modifier can be incorporated into the membrane by applying an aqueous modifier solution onto the wet gel membrane or immersing the gel membrane in an aqueous modifier solution.
Since the polymerization reaction for the preparation of polyacrylamide is a radical crosslinking polymerization as described above, the polymerization can be easily inhibited by the presence of oxygen. Therefore, the gel membrane should be prepared in the absence of oxygen. For this reason, a polyacrylamide gel membrane is generally prepared by a process involving: introducing an aqueous solution (gel-forming solution or gel solution) containing acrylamide, a crosslinking agent and a polymerization catalyst into a cell formed between two glass plates with a certain clearance (e.g., 0.3-1 mm); sealing the gel-forming solution from oxygen; and causing the crosslinking polymerization to prepare the desired gel membrane. This procedure employing glass plates are disadvantageous because the glass plate is easily breakable and rather heavy and careful handling is accordingly required. Thus, the above procedure employing the glass plates is difficultly utilized to prepare the polyacrylamide gel membrane in a mass scale.
For the reasons described above, it has been desired that the the glass plate for supporting the polyacrylamide gel membrane is replaced with a light-weight plastic material support. However, for the use of a satisfactorily acceptable plastic material support such as a polyethylene terephthalate (PET) sheet, poor adhesion between the gel membrane and the plastic material support should be improved, for the reasons given below.
The prepared polyacrylamide gel is horizontally or vertically placed for performing slab electrophoresis. The electrophoresis is performed for a certain period of time under predetermined conditions, and the desired analysis of the components originating from the living body is done after dyeing the electrophoresed gel membrane with Ponceau 3R (Ciba-Geigy), Coomassie Brilliant Blue G-250 (ICI), silver, etc. The gel membrane is apt to separate from the support in the dyeing procedure even in the case of employing the glass plate support. Accordingly, the dyeing procedure requires highly skilled operation to prevent the separation of the gel membrane from the support. The poor affinity of the plastic material support to the polyacrylamide gel membrane makes it more difficult to handle the element for electrophoresis without separation of the support from the gel membrane.